Inspired by the biological features of marine creatures, researchers in Singapore have developed seal-whisker sensors and soft-gel stingrays to measure the quality of sea waters in Singapore

The sea waters in Singapore are getting more colourful and vibrant. Inspired by the biological features of marine creatures, a team of researchers from the Singapore-MIT Alliance for Research and Technology (SMART) are studying the motion and sensing abilities of marine creatures to develop technologies in vehicles that are used to monitor and collect oceanographic data.

By mimicking their physical features, these researchers have designed “seal-whisker” sensors and “stingray” vehicles to help measure the quality of sea water in Singapore. Along with such vehicles, the team uses robotic kayaks to collect data from the sea, as well as flying drones to help monitor the water surface and coordinate the manoeuvring of these vehicles.

The team from the Water and Air Vehicles for Environmental Sensing (WAVES) laboratory at the Center for Environmental Sensing and Modeling (CENSAM) comprises scientists and engineers from the Massachusetts Institute of Technology (MIT), the National University of Singapore and the Nanyang Technological University. They are exploring better locomotion and sensing technologies to enable exploration in marine and other harsh environments.  

whisker sensor
Bio-inspired innovation – A whisker-like sensor to pick up cues from the surrounding water pressure

Seal-inspired whisker-like sensors

With their uniquely-shaped whiskers, harbour seals are able to detect the “wake” (underwater traces) of a fish up to several minutes after it has passed. Inspired by the seals’ whiskers, the WAVES researchers decided to create sensors that help underwater vehicles navigate and detect other vehicles and objects nearby. Each of the sensors is 3D-printed in the lab, allowing the researchers to produce them quickly while ensuring that the undulations on the sensors replicate the details of real seal whiskers. Attention to such details is vital in enhancing its capabilities.

These whisker-like sensors have significant advantages over conventional sensors such as sonars, acoustic navigation and underwater lights and cameras. First, they are inexpensive and cheaper to produce. Second, they use up a considerably smaller amount of power. Third, they do not harm aquatic animals in any way, unlike the loud and invasive sonars and other active sensing devices. The biggest advantage is that these whisker-like sensors can obtain feedback from their immediate vicinity and surroundings, removing the blind spots of conventional underwater sensors in collecting data. 

Typically, a small array of the whisker sensors is attached to the bottom of a robotic kayak. These self-moving kayaks collect sea water on the surface that are then sent back to the laboratory to measure water quality. The sensors provide feedback on flow conditions around the kayak, increasing its sensitivity in adapting to real-time changes in the water currents. For example, when the sensors detect opposing currents in close proximity, the kayak can change its direction quickly to avoid loading more vehicle fuel to tackle the force. In this way, by ‘feeling’ the flow around them, the sensors act as the ‘eyes and ears’ of the marine vehicles.

Professor Michael Triantafyllou (left), Principal Investigator, and Dr Pablo Valdivia y Alvarado (right), research scientist at CENSAM examining the whisker-like sensors attached to the bottom of an autonomous kayak.

Soft-gel rainbow stingrays

Similarly, when the researchers wanted to study the coastal conditions around the island, they looked at batoid fish commonly found in coastal marine environments, such as stingrays and manta rays, whose bodies move in a flexible wave-like motion as they swim about.

Taking a cue from these batoid fish, Dr Valdivia y Alvarado and his team have designed and built water vehicles encased in soft silicone bodies which feel rubber-like to the touch. These batoid-inspired robots are simple and more robust than traditional robots, which are usually made of discrete and stiff parts. More importantly, the flat shape and the natural vibrations of the soft body lend the robots more flexibility for motion. Smaller versions of the whisker sensors could also be attached to these vehicles to help control their movement.

“Instead of designing a very complex discrete mechanism, we use a flexible body with the right materials so that when you excite it, the natural vibrations that you see are basically the motions that you need to achieve,”

                                                          — Dr Valdivia y Alvarado, lead researcher of the team

Prototypes of the stingray vehicles on display at the WAVES laboratory.


Flying marine drones

To complement the robotic kayaks, the researchers deploy Aerial Unmanned Vehicles (AUVs) to provide a bird’s eye view of the sea, as well as Underwater Autonomous Vehicles (UAVs) like the stingray vehicles to capture information such as the temperature, pH level (acidity or neutrality of a substance), level of dissolved oxygen, turbidity (cloudiness or haziness of a fluid) and salinity of the sea water. Thus, data from aerial views, water surface and underwater are captured concurrently, making the process of real-time monitoring more efficient.

The kayaks and stingray vehicles are part of the robotic fleet that the WAVES lab team is developing to more efficiently survey and monitor the marine environment.

“Most technologies might work in the lab, but when you deploy them in the field, the probability of failure is much higher. Therefore, real breakthroughs and robust technologies are needed,” commented Dr Valdivia y Alvardo.

These bio-marine vehicles can be deployed more quickly than the conventional buoys, proving to be useful in the tracking and measuring of algae blooms since the masses of algae often disperse quickly. Harmful algae blooms may cause the oxygen levels in water to decrease sharply and lead to widespread death of marine life. In December 2009, a toxic bloom hit Singapore waters along East Johor Strait and caused massive fish kill and great economic losses1.

Follow the WAVES Lab team on one of their sea trials.


Modelling the marine ecosystem in Singapore

After gathering data from the field, another team at CENSAM will proceed to translate the collated data into predictive statistics and provide a realistic modelling of the marine ecosystem in Singapore. The work that these scientists are doing culminate in the development of a mobile robotic sensor network along the coasts and waters of Singapore.

The information derived from these measurements and models is shared with Singapore agencies for use in their day-to-day regulations and long-term planning. As the country continues to grow, more land will be needed to accommodate its human and industrial activities. Thus, surveying and monitoring the potential landfill areas will also be crucial in Singapore’s attempt to further reclaim land around the island.

“The marine environment is extremely challenging. We are making new tools to improve accessibility of the habour around Singapore, opening up new possibilities.”
                                                                                                         — Dr Valdivia y Alvarado

Right now, the team is studying exciting developments such as an octopus-type of propulsion and sensors that mimic the lateral line in fishes.

By looking toward nature for inspiration, the Singapore-based researchers demonstrate that problems faced by an urban city can be solved through innovative and efficient solutions.

This special science feature is produced by NRF Corporate Communications in collaboration with SMART CENSAM. All photos and videos are the property of SMART CENSAM. If you wish to reproduce/adapt the write-up or use the photos, please contact NRF at corpcom@nrf.gov.sg. 

About SMART                                                                                   
The SMART Centre is a major research enterprise established by the Massachusetts Institute of Technology (MIT) in partnership with the National Research Foundation of Singapore (NRF) since 2007. It is the first entity in the Campus for Research Excellence and Technological Enterprise (CREATE) developed by NRF.

The SMART Centre serves as an intellectual hub for research interactions between MIT and Singapore. Cutting-edge research projects in areas of interest to both Singapore and MIT are undertaken at the SMART Centre. SMART comprises an Innovation Centre and five Interdisciplinary Research Groups (IRGs): BioSystems and Micromechanics (BioSyM), Center for Environmental Sensing and Modeling (CENSAM), Infectious Diseases (ID), Future Urban Mobility (FM) and Low Energy Electronic Systems (LEES).


Using measurements from a variety of sensors and sensor networks, the Center for Environmental Sensing and Modeling (CENSAM) IRG aims to develop an accurate and predictive model of the natural and built environment of Singapore that seamlessly transits between different scales, from the level of a single building or facility to the level of the state, including the surrounding seas.

1 Monitoring Harmful Algal Blooms in Singapore: Developing a HABs Observing System Leong, Tkalich and Patrikalakis, 2012. 978-1-4577-2091-8/12 ©2011 IEEE